Develop Reference

Access the content of <ng-template>

Let us say that we have a child component that takes a template as an input :
In child.html:
<ng-container *ngTemplateOutlet=“formTemplate”></ng-container>
In child.ts:
#Component({
selector: ‘child’,
templateUrl: ‘./child.html’
})
export class ChildComponent {
#Input() formTemplate: TemplateRef<HTMLElement>;
}
In the parent component.html:
<child [formTemplate] = “tmpl”></child>
<ng-template #tmpl>
//some reactive form will be passed here
</ng-template>
In parent.ts:
#Component({
selector: ‘parent’,
templateUrl: ‘./parent.html’
})
export class ParentComponent {
}
The form is displayed correctly inside the child component.
Is there any way to access the form inside the child component ?
The child needs to access the form to perform some logic when the form is invalid for example.

How to Render Child Components Dynamically using loops if possible? (Angular 8)

I am trying to render my angular components dynamically using loops but I'm lost.
What I want to achieve is drag and re-arrange my components (I was able to achieve this using Dragula - ng2-dragula) but I want to save the arrangement to my local storage or session storage.
The tricky part is I am using child components
<section [dragula]="'VAMPIRES'">
<div class="first_element_class" id="first_element">
<my-first-component
[outputData]="outputData"></my-first-component>
</div>
<div class="second_element_class" id="second_element">
<my-second-component
[outputData]="outputData"></my-second-component>
</div>
</section>
I tried using the DOM sanitizer pipe to render them via for loops
import { Pipe, PipeTransform } from '#angular/core';
import { DomSanitizer, SafeHtml } from '#angular/platform-browser';
#Pipe({
name: 'trustHtml'
})
export class TrustHtmlPipe implements PipeTransform {
constructor(readonly sr: DomSanitizer){}
transform(html: string) : SafeHtml {
return this.sr.bypassSecurityTrustHtml(html);
}
}
Updated HTML Code (Let's assume I added my html elements to an array of object)
objectHTML: any[] = [{
toBeRender: `<div class="first_element_class" id="first_element">
<my-first-component
[outputData]="outputData"></my-first-component>
</div>`
}];
<section [dragula]="'VAMPIRES'">
<div *ngFor="let element of objectHTML">
<div [innerHTML]="element.toBeRender | trustHtml" ></div>
</div>
</section>
My question is is it really possible to render the html child components/elements using ngFor? I tried using the DOMSanitizer but I'm only getting a blank page (No error on console)

I have a similar solution for you. Firstly, in your <my-first-component> ts file declare "outputData" as #Input and use ngFor in HTML. Here is my sample code below.
CUSTOM Control
HTML: event.component.html
<h2>Event {{ event.id }}</h2>
<button (click)="event.hidden = true">Close me</button>
TS:event.component.ts
import { Component, Input } from '#angular/core';
import { Event } from './event';
#Component({
selector: 'my-event',
templateUrl: './event.component.html'
})
export class EventComponent {
#Input() event: Event;
}
export interface Event
{
id: number;
hidden: boolean;
}
**HTML:** app.component.html (You can use that code where you need to.)
<button (click)="addEvent()">Add event</button>
<div *ngFor="let event of events">
<my-event *ngIf="!event.hidden" [event]="event"></my-event>
</div>
Note: Here [event] is the #Input for your custom control and *ngFor is the loop.
TS: app.component.ts
import { Component } from '#angular/core';
import { Event } from './event';
#Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
events: Array<Event> = [1, 2, 3, 4, 5].map(i => ({id: i, hidden: true}));
addEvent() {
const event = this.events.find(e => e.hidden);
if (event) {
event.hidden = false;
}
}
}
Note: Please check the code and let me know. This code is also available in Stackblitz
LINK .

You can iterate with ngFor and render many times the child component by his selector.
components = [1, 2, 3, 4, 5];
<ng-container *ngFor="let component of components">
<child-component></child-component>
</ng-container>

Angular pass input variable to another component on button click

I come from a Python background, but I started trying to learn Angular and I'm really having trouble. Working between components is confusing to me and I can't figure it out. I made a good example that I think if someone helped me with it would go along way towards understanding Angular.
I just have two components: a "header" component and an app component. In the header component, I ask for the user's name and they click a button, and then it should show "Hello {{name}}" in the next component. I cannot get it to work to say the least and it's really frustrating. The Header part seems to work okay, but it's just not communicating with the other component at all. Neither the button part or the "name" part are working so I am clearly misunderstanding something I need to do when it comes to listening from the parent component.
Here is my Header HTML:
Name: <input type="text" id="userInput" value="Joe">
<button (click)=showName()>Show More</button>
Here is my Header TS:
import { Component, OnInit, Output, EventEmitter } from '#angular/core';
#Component({
selector: 'app-header',
templateUrl: './header.component.html',
styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
bodyDiv = false;
inputName = '';
#Output() buttonClicked = new EventEmitter();
constructor() { }
ngOnInit() {
}
showName() {
console.log('showName clicked.');
this.bodyDiv = true;
this.inputName = document.getElementById('userInput').value;
console.log(this.inputName);
console.log(this.bodyDiv);
this.buttonClicked.emit(this.bodyDiv);
this.buttonClicked.emit(this.inputName);
}
}
Here is the main Component's HTML:
<app-header (buttonClicked)='showNextComponent($event)'></app-header>
<p *ngIf="![hiddenDiv]" [inputName]="name">Hello {{ name }} </p>
Here is the main component's TS:
import { Component } from '#angular/core';
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
hiddenComponent = true;
title = 'show-button';
showNextComponent() {
console.log('Button clicked.');
this.hiddenComponent = false;
console.log(this.hiddenComponent);
}
}
So who can show me what I'm doing wrong and help figure out Angular a little better? :) Thank you!

replace showName function with below code :
showName() {
console.log('showName clicked.');
this.bodyDiv = true;
this.inputName = document.getElementById('userInput').value;
console.log(this.inputName);
console.log(this.bodyDiv);
this.buttonClicked.emit(this.inputName);
}
replace below code in your main component.
name:string
showNextComponent(value:string) {
this.name = value;
}
replace below code in your html :
<app-header (buttonClicked)='showNextComponent($event)'></app-header>
<p *ngIf="name">Hello {{ name }} </p>
Please let me if you have any question and I would suggest try to use ngmodel or something else instead of directly communicating with the DOM.

Here is a slightly modified and working sample: https://stackblitz.com/edit/angular-jhhctr
The event emitter in the header component emits the name (string) which is the $event in showNextComponent($event). You have to capture this in the main component and assign it to a local variable to be able to use it in the main component's template as {{name}}
[inputName]="name" is incorrect. You can pass values like that to angular components not to actual HTML DOM elements.

There are couple of ways to communicate from one component to another in angular - Using #Input()in your child component will expects an input from parent component and #Output() from your child component will emit an event from the child component
So in your case if you want to pass a value from parent to child you need to use input property or decorator on your child property - I will provide you the code but just go through proper guidance from the link provided this will make you to create better angular applications https://angular.io/guide/component-interaction
First you need to swap your components your header component should be your parent and the child component will be your main component - if you want to work in the same way just move your codes vice versa
Header html
Name: <input type="text" id="userInput" name='userInput' [(ngModel)]='inputName' value="Joe">
<button (click)=showName()>Show More</button>
<div [hidden]='bodyDiv'>
<app-header [bindName]='inputName'></app-header>
</div>
Header Component
import { Component, OnInit, Output, EventEmitter } from '#angular/core';
#Component({
selector: 'app-header',
templateUrl: './header.component.html',
styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
bodyDiv = true;
inputName = '';
constructor() { }
ngOnInit() {
}
showName() {
bodyDiv = false;
}
}
Main Component Html
<p>Hello {{ bindName }} </p>
Main component ts
import { Component, Input } from '#angular/core';
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
#Input()
bindName: string;
}
In your header component the inputName property will be binded using two way data binding where i used [(ngModel)]='inputName' so whatever you enter in the input text it will be updated in your inputName property
Now we need to do only one thing just to show your child component with any event - so when the button is clicked the div with [hidden] property will be false and it will be displayed and as we pass the inputName to the child Component it will be updated
And finally the child component will be displayed and the input written in the text will be updated in the child component - when the child component html displays the bindName will be updated and there will be result you expected
That's all I think this should work well - Try this and let me know - Thanks Happy coding !!
Don't forget to look into the link above where you can see many types of component interactions

How can I access an already transcluded ContentChild?

I have a angular component app-b that is used within a component app-a that is used in the app-component. The app-component has some content in app-a, app-a transcludes this with ng-content into app-b, app-b shows it with another ng-content - but how can I access this content within the component (and not it's template)?
I would think that ContentChild is the correct approach but appears to be wrong.
Example:
https://stackblitz.com/edit/angular-ddldwi
EDIT: Updated example

You cannot query by tag name with #ContentChild decorator. You can query either by template variable, component or directive selector.
app-a.component.html
<app-b>
<ng-content></ng-content>
<p #myContent>This is a content child for app-b.</p>
</app-b>
app-b.component.ts
import { Component, AfterContentInit, ContentChild } from '#angular/core';
#Component({
selector: 'app-b',
templateUrl: './b.component.html',
styleUrls: ['./b.component.css']
})
export class BComponent implements AfterContentInit {
#ContentChild('myContent') contentchild;
ngAfterContentInit() {
console.log(this.contentchild);
}
}
Live demo

I recommend sharing the data between components. For example, move your data (E.G. dummyName) into a service. Then add the service to each component (where you need the shared data).
Service:
import { Injectable } from '#angular/core';
#Injectable()
export class DataShareService {
public dummyName: String = 'one';
constructor() { }
}
Add the new service to app.module.ts:
providers: [DataShareService],
Child Component:
import { DataShareService } from './data-share.service';
import { Component } from '#angular/core';
#Component({
selector: 'app-child',
templateUrl: './child.component.html'
})
export class ChildComponent {
constructor(public ds: DataShareService) { }
toggle() {
this.ds.dummyName = this.ds.dummyName === 'one' ? 'two' : 'one';
}
}
Child Component template (html):
<p> {{ds.dummyName}}</p>
<button (click)="toggle()">Click Me to Toggle Value</button>
Parent Component:
import { Component, OnInit } from '#angular/core';
import { DataShareService } from './data-share.service';
#Component({
selector: 'app-root',
templateUrl: './app.component.html'
})
export class AppComponent {
constructor(public ds: DataShareService) {}
displayNumber() {
return this.ds.dummyName === 'one' ? 1 : 2;
}
}
Parent Component template (html):
<p> this is the parent component:</p>
<div> value as string: {{ ds.dummyName }} </div>
<div> value as number: <span [textContent]="displayNumber()"></span></div>
<hr>
<p> this is the child component:</p>
<app-child></app-child>
Note! The child component toggle() function demonstrates how you can change the data. The parent component displayNumber() function demonstrates how to use the data, independent of it's display (I.E. as just pure data).

This appears to be impossible due to a bug in Angular:
https://github.com/angular/angular/issues/20810
Further reference:
https://www.reddit.com/r/Angular2/comments/8fb3ku/need_help_how_can_i_access_an_already_transcluded/

Angular2 ngFor not working

I am trying to implement a basic shopping list, but my ngFor in Angular is not working.
import { Component, View } from 'angular2/angular2';
#Component({
selector: 'my-app'
})
#View({
template: '<h1>{{title}}</h1><ul><li *ngFor="let i of items"><span>{{i}}</span></li></ul>'
})
export default class MyAppComponent {
title = 'ShoppinList';
items = ['Milk','Ham','Eggs'];
}
The only thing that appears is "loading..." and I am getting more than 10 cryptic errors.

Without trying it first I noticed an error in the import statement at the top. Should be:
import { Component } from '#angular/core'

#View() was removed almost a year ago. If you see examples that use it, just move the content to the #Component() decorator while directives and pipes were moved from #Component() to #NgModule()s declaration.
You need to add CommonModule to #NgModule({ imports: [CommonModule], ...}) export class SomeModule{} in every module where you want to use ngFor (or other directives shippled with Angular - BrowserModule already includes CommonModule).

its good way to use ngIf and use your template inside your component properties.
import { Component, View } from 'angular2/angular2';
#Component({
selector: 'my-app',
template : '<div>
<h1>{{title}}</h1>
<ul *ngIf="items">
<li *ngFor="let i of items"><span>{{i}}</span></li>
</ul>
</div>'
})
export default class MyAppComponent {
title : string = 'ShoppinList';
items : Array<string> = ['Milk','Ham','Eggs'];
}

You don't have to use #View here.
#Component({
selector: 'my-app',
template: `
<div>
{{title}}
<ul><li *ngFor="let i of items"><span>{{i}}</span></li></ul>
</div>
`,
})
export class App {
title = 'ShoppinList';
items = ['Milk','Ham','Eggs'];
}
Working plunker